Dry etching method for selectively etching silicon nitride existing on silicon dioxide

摘要

A dry etching method for selectively etching a silicon nitride having the generic formula SixNy existing over a base of SiO2 utilizing, as the etchant gas, a mixture of a fluorohydrocarbon in which the atomic ratio of F/C is smaller than 3:1, the mixture containing 30-70% of CO2 on a flow rate basis. The presence of such a large amount of CO2 in the etchant in combination with the particular fluorohydrocarbons is effective for enhancing the selective ratio of etching between SixNy and SiO2 and also for preventing formation of obstructive polymers of fluorocarbons.